The present invention relates generally to semiconductor devices and fabrication methods and more particularly to containers for storing and transporting slurry used in the fabrication process.
Surface finishing is utilized in many arts for the polishing and/or planarization of particular devices. For simplicity, the term xe2x80x9cpolishingxe2x80x9d will be used to include both polishing and/or planarization. One example of an application where polishing is performed and in multiple processing steps is in the manufacturing of semiconductor devices.
Chemical-mechanical planarization (CMP) is a technique widely used in the fabrication of semiconductor devices. CMP is performed by introducing a polishing fluid or slurry between a working surface and a polishing article, such as a wafer, and then moving the wafer and device relative to one another, most often by rotating. The slurry generally comprises abrasive particles which mechanically and chemically remove material. The chemical components of the slurry chemically alter the film being polished. The slurry along with the tool parameters planarize the surface of the semiconductor wafer. In the CMP process, it is important to control the particle size of the slurry. As an example, in the fabrication of semiconductor devices, in many applications the typical particle size is 50-200 nm. It is undesirable to have too large of a particle size since the larger particles can cause scratching to the polished surface. Too small of a particle size will have inadequate material removal rate. Scratching of the polished surface during manufacturing will lead to decreased device yields.
One source for larger particle size in a slurry mixture that has been noted by the inventors of the present application is the container which holds the slurry used in the manufacturing process. The containers often called totes or drums are commercially available in a number of different sizes, common types are in 55 gallon or 250 gallon sizes. The containers are filled with the slurry at their origination locations, by the slurry manufacturer and then transported to other sites for use, such as to the integrated circuit manufacturer. A problem identified in this process is that a portion of the slurry can dry inside of the container, such as along the container walls, due to movement of the slurry into air pockets inside of the container. The dried slurry can then mix with the liquid slurry mixture, such as by flaking off from the side walls, which results with larger sized particles contained in the slurry mixture. Some slurries have been shown to dry in less than five minutes exposure to air. There have been attempts made to correct this problem by minimizing transfer time and container agitation. In these situations, the desire is to limit the transport time before the slurry can begin to dry and to limit agitation so that the slurry liquid mixture will not splash or otherwise flow up along the side walls. These attempts have not produced satisfactory results. Also, filtering is used to eliminate the larger particles as the slurry is sent to the distribution system. Filters, however, are not one hundred percent effective.
There is a need for a new slurry transport container which eliminates or at least minimizes the air space or pockets inside of the container.
The present invention provides a container adapted for receiving slurry and which includes means for reducing air space inside of the container.